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hot attic solutions - DTisme - 06-12-2011
We have an "out building" with 2 rooms, one of which I work in every day. There is a full attic above both rooms. One room was built with that reflective barrier stuff on the other side of the ceiling drywall. The one I work in has diddly squat. The diddly-squat room is HOT. The other room is warm. I'd like both rooms to be cooler, so I'm thinking this reflective barrier stuff is not what I want, though I'd be willing to add it to diddly-squat room just to make them both the same.
SO -- what ELSE can I do? Clearly, whoever built this house did not insulate the roof.
I assume the answer is some kind of attic fan, and I've seen the ads in the paper for solar attic fans. Has anyone out there any experience with these? What about those turbine thingies where the hot air rising turns the turbine and expels the air? Can you use them with these metal roofs?
What will give me more bang for my buck? What will give me the coolest rooms? (short of an AC!) btw, both rooms also have ceiling fans. Which barely help. I have to sit right in front of an additional fan if I want relief.
RE: hot attic solutions - Carey - 06-12-2011
We have a solar gable mount fan on the Ohana (as we have a gable end on the ohana attic).
We added the ReFlectix radiant barrier prior to the attic fan, and then added the solar attic fan, each step has helped, but working in the attic is still toasty - in the ohana, it is cooler (and we do have an area in the shower that has an opaque skylight, with no radiant barrier .... the floor is nice & toasty right there, ....good for a shower....but it does remind us how nice the radiant barrier is...)
We chose the gable mount because we did not need to pierce the metal roof or worry about the metal roof flashing dilemma (see other threads on that...) and it was available at Lowes & very easy to install in the attic.
One other thing that is major.... do you have enough window/door (screened) space....esp on the tradewind side..... we have found that adding more tradewind side windows has helped (and shading windows that get the afternoon sun)
RE: hot attic solutions - hotinhawaii - 06-13-2011
The radiant barrier will give you the most bang for the buck, however, you should install it closer to the roofing. If you place it on the underside of the rafters or even between the rafters (allowing at least 3/4" between the barrier and roofing) it will keep the attic air cooler thereby keeping the room below cooler. The other advantage to this method is that the barrier will not become dirty or corroded nearly as fast. If the barrier above the drywall is laid flat, any dust in the attic will settle on it, decreasing it's effectiveness significantly.
What color are the exterior walls to the house and do they get direct sunlight at all? If they do, adding radiant barrier to those walls will also help. If they are just bare studs, place it on the interior edges of the studs and cover with drywall, or between the studs.
RE: hot attic solutions - DTisme - 06-13-2011
Ooh, wish I had me some bare studs!* Unfortunately, all walls are already finished walls. Building is painted light gray. As far as windows, the cooler room w/the radiant barrier has 3 large windows on 3 walls, definitely tradewind side, and that's another reason that room is cooler. My office has two large windows, screened, natch, but hardly gets the crossflow air. I think this place was built by monkeys.
I totally see the advantage of the radiant barrier under the ROOFING vs. over the CEILING. Still, what about good ol' fashioned pink fiberglass attic insulation?
Will look into these solar gable fans. Do you think those are the ones that are advertised in the Tribune Herald? Carey, if you have a minute, can you post a link to the one you got at Lowes? Do you have just the one fan? Would it be prudent to have one at each gable end? As I recall, there's even a WALL up there in between the two sides of the attic. I think once upon a time the ex-owners used half of it for storage.
*Get you mind out of the gutter!
RE: hot attic solutions - DTisme - 06-13-2011
Carey, is this what you used? http://www.lowes.com/pd_41125-228-SG8_0__?productId=3033209&Ntt=attic+fan&pl=1¤tURL=%2Fpl__0__s%3FNtt%3Dattic%2Bfan&facetInfo=
RE: hot attic solutions - Carey - 06-13-2011
That link looks a lot like the fan...(it was a little less $$, but that was a 3-4 years ago...)
We only have one, because our ohana is attached to the carport of the main house on the other gable side.... & we haven't worked out the best way to deal with vents in a carport (gut feeling, it is a no-no). The main house has raised ceilings, and does not have attic space.
Oh, also make sure you have enough eave ventilation, that is where the cooler air will come in, those little "bird holes" are for the birds, unless your block boards are peppered with them! There are a number of links for calculating the free vent space you need, here is a link to the GAF calculator (one of my old clients...so I use theirs, but there are others...):
http://www.gaf.com/Roofing/Residential/Products/Roof-Vents/Ventilation-Calculator/Ventilation-Calculator.aspx
Link on how to calculate the 1/300 or 1/150:
http://www.gaf.com/Roofing/Residential/Products/Roof-Vents/Attic-Vents-Roof-Ventilation.aspx
We installed our Reflectix in our upper rafters - hubby squinched (techy term;~) around up there on a couple sunny days, I think we could pour him out after that.... if we ever do much work up there again, we will make sure to install attic stuff on cool, very overcast days.
RE: hot attic solutions - hotinhawaii - 06-13-2011
Fiberglass insulation (the pink stuff) will only help a little. Consider that the outside temperature and the temperature you would like inside are only going to be a few degrees apart, so what heat are you trying to keep where? If you keep the attic and its air cooler by using a radiant barrier (which will shave 15-20 degrees off the temperature there) and possibly a solar fan, there isn't much need for the pink stuff. It will make the rain noise less though.
RE: hot attic solutions - hotinhawaii - 06-13-2011
One more thing, fiberglass insulation does almost nothing to block radiant heat which is the main problem you are trying to address. The only things which block radiant heat are reflective barriers or objects with great thermal mass like concrete or thick wood or water or water-containing objects like tree leaves.
RE: hot attic solutions - DTisme - 06-14-2011
Wow, thanks all! Lots of great info!!
Now that I'm getting into the research, I'm looking at specific solutions...
There's this kind of thing...
http://www.lowes.com/pd_41125-228-SG8_0__?storeId=10151&Ntt=solar+attic+fan&UserSearch=solar+attic+fan&productId=3033209&N=0&catalogId=10051&langId=-1 (can't tell how much power the panel puts out)
and this...
http://www.amazon.com/Ventamatic-VX2515SOLARGABLE-Ventilator-12-6-Watt-18-Volt/dp/B001AHAJSK/ref=sr_1_3?ie=UTF8&qid=1308108305&sr=8-3 (12.6 watt, 18 volt motor)
Or on-roof solar fans like...
http://www.homedepot.com/h_d1/N-5yc1v/R-202321540/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053
OR, simply an old-fashioned heat-driven attic turbine like...
http://www.homedepot.com/h_d1/N-5yc1v/R-202321455/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053
Clearly, cutting into the roof would be a big pain in the butt (vs. gable mount), and therefore more expensive to install, but I want what will make me the most comfortable. I also wonder whether we might have to get two of whatever we do get. (I have a feeling I'd need two - the attic is divided by a frickin' WALL and each side is 20x20.
Anyone think one of these has any advantage over the others? Do the plain-old heat-driven turbines work or is it worth it to invest in solar unit(s)?
RE: hot attic solutions - hotinhawaii - 06-14-2011
I hope you will try the radiant barrier installed as suggested before going to the expense of an attic fan. An attic fan will do nothing to prevent the heating of the room below the attic by radiant heat. The sun's energy will come through the roof and ceiling and warm any objects in the room including the floor, furniture, etc. Those warm objects will then warm the adjacent air thereby heating the air in the room to an uncomfortable level. The attic fan will do nothing to help this. And this is the main cause of the heat in the room.
My first experience with radiant barrier was in a brick home in Baltimore. I had a thick black slate roof. The attic temperature was normally above 120 and the second floor of my house was about 15 degrees warmer than downstairs in the summer. It was awful. I installed radiant barrier on a rainy day. Voila! The upstairs was now no warmer than downstairs and the attic was bearable on a sunny day. I am a believer. And I hope to make you one too!